I'm not to sure if this belongs here but. . . I give guitar lessons and my mom said that you have to be a "certified guitar instructer" and it's illegal if you do even if i'm just giving guitar lessons locally. I know a guy who just teaches chords for pretty much an hour and he pretty much knows nothing on music theory. Is this true? . . . Stupid question but yeah :P
I don't know why it would be illegal to teach someone to play an instrument without a 'license' or a certification. Probably one of the dumbest things i've ever heard in my life. Its not like you can do irreparable damage by teaching someone something untrue about the instrument.
As long as you are not selling yourself and advertising yourself as a PROFESSIONAL teacher, then I see no harm in it. You can even make a profit out of it, but like I said you can't claim you are a professional.